1. Field of the Invention
This invention relates to hydraulic jet cleaning in wellbores, and more particularly, to a jetting tool which is switchable from a down-jet to a-side-jet configuration.
2. Description of the Prior Art
The buildup of materials on the inside of well casing or tubing is a common problem. It is known that many wells in some areas have buildup problems severe enough to eventually plug the tubing, and this problem may occur in both production and injection wells.
Common compounds causing such buildup problems are barium sulfate, silicates, calcium carbonate, calcium sulfate, carbonate, sulfate, silica, water scale with hydrocarbons, coke tar, coke and complexes, wax and complexes, paraffins, sludges, muds and gels.
Many different methods have been used to remove material buildup. For example, one method of dealing with paraffin buildup is to melt the paraffin with hot oil. Hot oil units heat crude oil, and the heated oil is circulated into the well. Hot water has also been used to melt and remove paraffin and also to remove salt. While in many cases this technique is successful, it does have the disadvantage of requiring considerable energy to heat the oil or water, and it is not useful in removing other materials which will not melt from the heat or which are not water soluble.
Chemicals may also be used to dissolve paraffin deposits. This may eliminate the problems of heating, but the chemicals may require special handling because they are usually highly flammable and toxic.
Other methods used to remove buildup include Dyna-Drills run on coiled tubing, milling with jointed tubing, acid washing, and broaching with a wireline.
To avoid the problems of removal of buildup by hot oil or water or by chemicals, jet cleaning was developed to utilize high pressure liquids to remove the materials by erosion. Coiled tubing service companies have performed jet cleaning jobs for many years. Generally, these jobs have been limited to removing mud cake, paraffin or packed sand. The jet cleaning tools of this type are usually made of heavy wall mechanical tubing with a plurality of holes of various diameters drilled in a symmetrical pattern around the tool. Water was used as the cleaning media. Job results were usually unpredictable, and it has been necessary on many occasions to change out the production tubing string. Accordingly, there is a need to efficiently and thoroughly clean material buildup in well casing or tubing.
The Otis Hydra-Blast.RTM. system was developed to address these problems by providing an economical means of cleaning buildup deposits from downhole tubing. This system utilizes high pressure fluid jet technology in conjunction with the economy and efficiency of coiled tubing. The Hydra-Blast.RTM. system includes an indexing jet cleaning tool, an in-line high pressure filter, a surface filter unit, a circulation pump with tanks and a coiled tubing unit. It also utilizes a computer program to design the actual cleaning jobs for any particular situation. The optimum jet size and number, retrieval speed and number of passes is calculated to accomplish a successful job, and this is particularly important in trying to remove harder materials such as the harder barium compounds. In general, this system may be described as a water blasting system which directs high pressure streams of water against the buildup to remove the material by the eroding or cutting action of moving fluid.
In a typical application of the Hydra-Blast.RTM. system, the operator uses a cleaning tool which at least in part utilizes a downward stream to cut into the material as the tool is lowered into the tubing. This is referred to as "down jetting" or "down blasting." In addition to downwardly directed jetting ports, there may be ports directed at any angle, including perpendicular to the longitudinal axis of the tool. This tool is particularly well adapted for cutting a path into any buildup which has closed off the tubing completely or which has reduced the diameter of the tubing such that the tool cannot enter the buildup area. However, the down-blast tool, even with side jetting ports is not particularly well adapted for removing large amounts of buildup along the walls after the tool is free to pass therein. The amount of fluid jetted to the side is not sufficient by itself to remove some deposits. In such cases, the original down-blast tool is removed from the well, and an additional well trip is made with a side-blast jetting head designed specifically for the purpose of providing jets directed against the buildup on the walls of the tubing. This two-step process works well, but the additional trip in and out of the well on the coiled tubing string is expensive. Additionally, in some cases, the first trip with a down-blast tool is not necessary at all, but this is generally not known until a down-blast tool is run into the tubing. Therefore, a need exists for a tool which can provide down blasting, but also can provide side blasting with only a single trip into the well.
The apparatus of the present invention solves this problem by providing a tool which allows down blasting as the tool is run into the tubing string and which may be switched to a side-blast tool without removal from the wellbore.